docs: def format_subpages(self, page, subpages):
          """Banana banana
          """
          if not subpages:
              return None
  
          try:
              template = self.get_template('subpages.html')
          except IOError:
              return None
  
          ret = etree.XML(template.render({'page': page,
                                           'subpages': subpages}))
          assets = ret.xpath('.//*[@src]')
          for asset in assets:
              self.__lookup_asset(asset, self.extension.project, page)
  
          return ret